1. Field of the Invention
The present invention relates to a motor control apparatus.
2. Discussion of the Background
Control apparatuses for alternating-current (AC) motors, specifically, servo controllers for AC motors, generally have a triple-loop configuration. Specifically, a feedback loop of a position control system and a feedback loop of a speed control system constitute a double-loop configuration, combined with a current feedback loop including power conversion by pulse width modulation (PWM) and d-q coordinate system conversion, resulting in a triple-loop configuration. In a current control system, in view of a torque of the motor developing in proportion to current, a torque command is input from the speed control system.
As disclosed in WO2005/093939, the disturbance rejection control system includes an inertia variation inhibitor to estimate a disturbance torque based on a first torque command and an actual detection speed of the motor. The inertia variation inhibitor then adds the disturbance torque to the first torque command and inputs the sum to the current control system as a second torque command. Attempts have been made to improve robustness against a greater moment-of-inertia ratio. Specifically, WO2005/093939 discloses a first phase compensator and a second phase compensator. The first phase compensator creates a new speed command having a phase advanced by introducing an initial speed command, and then outputs the new speed command. The second phase compensator creates a new speed command having a phase advanced by introducing a detection speed of the motor and a torque command, and then outputs the new speed command as an error target command.